N-methylated phenylene diamines as rich mixture additives



was! Patented Apr. 20, 1954 UNITED S S FFICE F"? ar N-METHYIIATED PHENYLENE DIAMINES AS RICH MIXTURE ADDITIVES Joseph- C. Firey, Richmond, and Edward 3. McLaughlin, El...Cerrito, Calif., assignors to California Research Corporation, San Francisco, Calif., a corporation of Delaware No Drawing; Application December 19, 1950, Serial No. 201,701

7 .Claims.

This invention relates toaspark.ignitiontengine. fuels; more particularly, .to spark ignition engine fuels boilin in the .gasoline boiling range and having improved anti-knock characteristicsunder rich mixture conditions and :to a methodrof producing such fuels.

In an attempt to reachisa' level of higher :power output of a gasoline engine before .knockingoce curs, it has becomethe practice to 'supercharge the engine. However, supercharging, asza means of obtaining increased power. "output, :is'limited.

A given fuel can tolerate only a certain amount.

of supercharging, beyondwhich it knocks excessively. By employing rich fuel-air mixtures, that is, fuel-air mixtures -in whi'ch--the...propor+ tion of fuel to air is in excess of thatreqriired for complete combustion,-.a greater. amount of supercharging ;can be tolerated with argiven fuel than if a lean mixture iswemployed. This-expedient also has its limitations in that :whena certain richness is reached, the enginemisfires and power output drops oif.

In an effort to increase the'power: output still further before knocking occurred. numerous anti-knock agents have been addedto the base fuel. Tetraethyl lead has been one oi the most important of the anti-knock agents WhiChxihEtS.

been added to spark ignition engine fuels. Such other agents as have been proposed are, for the" most part, less effective than te'traeth-yl .lead or are more expensive. tetraethyl lead, its useuis *disadvantageous'owing to several factors, such as itstoxicity: and its tendency to deposit lead compounds in carburetors, manifolds, valves, cylinders .or exhaust pipes.

In still further efiorts to increase thepower of an engine before knocking foccurred, special base fuels of high anti-knock:properties were'manua factured by cracking, isomerizationwof straightchain to branched chainhydrocarbon -and .al-'

kylation of isoparafiins with olefins. Judi-cious blending of stocks so prepared-with .oneranother and/or with straight run distillates has'also contributed to upgrading'base fuelsz Even when anti-knock agents have been added -ato special Despite the advantages of Also, the disadvantages inherent in the use of tetraethyl'lead still remain.v

Fuels of the gasoline type have been rated'by the CFR-ASTM-D35'T-43T method and the CFR,'ASTM-D6l4.-43T method. These methods? are commonly known as and hereinafter referred. to as the F-2 and the F-3 methods, .respec tively. These methods have rated fuels dependably for lean mixture use, i. e., use under normal or cruising conditions, but they are notdependable for rating fuels for use in supercharged engines using rich mixtures, as'inaircrait take-.ofi and climbing.

or better by the F-2 and F-3 methods have proved to be inferior fuels under conditions of extreme power requirementswhere the engine is supercharged and a rich fuel-air mixture is used.

The failure of the above methods .to rate fuels dependably for certain purposes has led :to the development of. another method, designated as the CER-TAFD-FQ-AeB :method, hereinafter called-" the F-t method, described in a report by the Coordinating Research Council dated April 20,

1943, and entitled, CFR Superoharge Methodiof Test for Knock Characteristics of Fuels.

used, rates a fuel under conditions of supercharging and rich fuel-air mixtures and itcorrelates well 'withtfull-scale ratings of fuelsnas in" aircraft take-off andcli nbing. The engine em- .ployed is a single cylinder, liquid-cooled, gaso-- line spark ignitionengine; the cylinder is the Under these latter conditions, many fuels that have been rated as :octane.

Aviation. This method, the description of which. has been widely circulated and which :is Widely same as that used in the F-2 method of rating fuels; manifold fuel injection is employed; the engine is equipped for supercharge; the compression ratio is 7:1; and the engine is operated at 1800 R. P. M., 375 F. jacket temperature, 225 F. air temperature, and spark advance BTC. Further details as to design and operation can be obtained from the above-mentioned report.

Ratings by the F-4 method are given herein in terms of octane number up to 100 octane, and, above 100 octane they are given in performance numbers and as equivalents of isooctane 14 milliliters of tetraethyl lead per gallon of fuel, at being a positive number, usually of the order of 1 to 10. For convenience, hereinafter F-e ratings will be referred to as so many octane units (e. g., 98 octane units) where the fuel rated is not more than the equivalent of pure isooctane (which has an octane number of 100) and, where the fuel rated is more than the equivalent of isooctane, as performance numbers and as S-i-n (e. g., 8+ 1.0), where S stands for isooctane and n for the number of milliliters of tetraethyl lead required to be added to isooctane to produce a fuel having the same F- value as the fuel rated. (The number of milliliters of tetraethyl lead, n, means n milliliters of the compound Pb(C2H5)4.)

The performance number is used to designate the relative knock-limited power output of fuels having octane numbers above 100 when tested according to the F-4 procedure. Isooctane (having an octane number of 100) has a performance number of 100. A fuel having a performance number of 150, for example, has a knock-limited power output 1.5 times that of the fuel having a performance number of 100.

It is an object of the present invention to pro vide anti-knock agents for spark ignition engine fuels, and to provide motor fuels containing them, which agents are inexpensive, adequately soluble in gasoline and lack the disadvantages of tetraethyl lead.

It is a particular object of the present invention to provide a method of obtaining, and to provide motor fuels having superior rich mixture ratings, without entire reliance upon selection of base fuel and the use of large amounts of tetraethyl lead.

It is a further particular object of the invention to provide unleaded spark ignition engine fuels having high anti-knock and especially high F-4 ratings.

It is a still further object to provide a gasoline type of fuel for aircraft engines which provides improved anti-knock characteristics under conditions of supercharging and use of rich fuel-air mixtures.

In accordance with the invention, N-methylated phenylene diamines are incorporated in a base fuel comprising substantially gum-free hydrocarbon fuels boiling in the gasoline boiling range in amount sufficient substantially to increase the anti-knock value of the base fuel.

The N-methyl phenylene diamine used in accordance with the invention maybe N methyl-p-- phenylene diamine; N-methyl-o-phenylene diamine; N-methyl-m-phenylene diamine; N,N- dimethyl-p-phenylene diamine; N,N-dimethylo-phenylene diamine; N,Ndimethyl-mand p--phenylene diamine; or a nuclear alkyl homolog of any of these diamines, containing one or more nuclear C1 to C4 (inclusive) alkyl substituents. Examples of the homologs are: N,N-dimethyl- 1,2-diamino-4-methylbenzene; N,Ndimethyl- 1,4 diamino 2 isopropylbenzene; 4 methylmore of the above and other types of fuels.

4 amino-2-methyl aniline; and N,N-dimethyl-1,3- diamino-G-methylbenzene.

Instead of a single phenylene diamine, mixtures of two or more may be used; and commercial mixtures containing other amino compounds, not of the invention, but predominating in diamines of the invention, may be used. Also, phenolics or amino phenolics may be used. In addition to the phenylene diamines, other compounds may be added to the fuel;' other agents such as pour point depressants, ketones, alcohols, esters, aliphatic amines, and other stabilizing agents. Other agents may be used to improve the quality or the octane numbers of the fuel; such agents may be used as tetraethyl lead, aromatic amines (e. g., amino phenolics, phenolics and phenyl amine), iron carbonyl and the like.

The base fuel of the invention may be a substantially gum-free (i. e., substantially free of gumforming constituents such as olefinio hydrocarbons, e. g., monoolefins and diolefins, etc, commonly believed to be the primary cause of gum formation) hydrocarbon fuel boiling in the gasoline boiling range; that is, having an ASTM (D-86) distillation with an initial boiling point of about F. and a final boiling point of about 400 F. Preferably, however, a petroleum base fuel is employed which may be a straight-run petroleum distillate, a petroleum distillate catalytically recracked to convert olefinic constituents of the distillate, an alkylate (e. g., sulfuric acid or HF isoparafiinolefin alkylate), an arc matic fuel (e. g., cumene, toluene, mand p-xylene etc), a catalytically reformed gasoline,

a natural gasoline, hydrogenated polymers (e. g.,

polymers of butene which upon regeneration have characteristics of isooctane, etc), isopentane or butane, a specific hydrocarbon (e. g., 2,2,3-trimethylbutane, etc.) or a blend of two or Most advantageously, a base fuel is employed boiling within the range above prescribed, which is derived from petroleum (such as straight run distillate-sulfuric acid alkylate-isopentane blend), is substantially stable to oxidation (i. e., does not oxidize readily upon standing; does not readily form gums or polymerization products, or lose color upon standing), and has a clear (no lead or other anti-knock additive present) F-Z octane number not less than 80. Another somewhat equally suitable hydrocarbon base is a blend of straight run gasoline, aromatic hydrocarbons (e. g., pand m-xylene) alkylate, and isopentane or butane. Other specific blends which may be advantageously used to form the hydrocarbon portion of this invention include blends of straight run gasoline, retreated catalytically cracked hydrocarbons, hydrogenated polymers, natural gasoline, catalytically reformed gasoline, and isopentane or butane.

The phrase substantially gum-free as used herein and in the appended claims is intended to mean that the raw hydrocarbon portion of the composition of the invention shall not con tain gum in amounts greater than about 6 milli- 1 grams per 100 milliliters as measured by ASTM method 13381-49 (existent gum in gasoline) or by ASTM method D873-49 (oxidation stability of aviation gasoline). As commonly practiced in the industry, gum inhibitors are not added to raw hydrocarbons boiling in the gasoline boiling range containing gum not greater than about 6 milligrams per 100 milliliters. This is primarily based upon the relative ineffectiveness of known gum inhibitors to inhibit such small.

amounts of gum and that such small amounts of gum do not generally cause difficulties in engine operation.

It is generally desirable to add small amounts of tetraethyl lead stabilizers when it is a component of this invention to prevent deposition of the lead and, even more important, to insure effective utilization of the tetraethyl lead in the combustion chamber of the engine.

Tetraethyl lead may be added to the hydrocarbon portion of the base fuel to form the base fuel of this invention in minor amounts sufiicient to raise the F-2 octane number of the hydrocarbon blend above at least 100. It is generally preferred. not to add more than about 6 cc. of tetraethyl lead per gallon of fuel. It is generally preferable to add not more than about 4.6 cc. per gallon of base fuel, and, in many instances, about 3 to 4- cc. of tetraethyl lead per gallon or less may be suflicient.

The diamines of this invention may be used in amounts sufiicient to improve the anti-knock value (the octane number) of the spark ignition engine fuel when used at conditions of rich fuelair mixture, the amounts ranging from about 0.1 to by weight, based on finished fuel, amounts not less than about 0.3% being preferred.

Blending of the diamines of this invention with the base fuels is simple, comprising merely mixing the diamine and the base fuel together with such heat and/or agitation as is necessary.

The base fuels of this invention may be unleaded (no tetraethyl lead) or leaded. The unleaded fuels offer the advantage of improved anti-knock ratings without the deleterious effects of tetraethyl lead. On the other hand, the leaded fuels are especially useful as premium grade rich mixture fuels. To illustrate, a base fuel having a clear octane rating (F-2 method) of 80 may be taken as the base fuel. In order to exemplify the advantages of using a phenylene diamine, tetraethyl lead (4 ml. per gallon) is added to the base fuel to increase the octane rating (F-2 method) to 100 or more, then a diamine (or a mixture of diamines) of the invention may be added in quantity; e. g., 0.3% by volume (based on final fuel) of N,N'-dimethyl-p-phenylene diamine, sufficient to produce a finished fuel having an i -i rating of S+2.0 or more.

The method of this invention obviates the disadvantages inherent in othe use of large quantities of lead (e. g., the deposition of lead compounds in carburetors, manifolds, valves, cylinders or exhaust pipes, and the toxicity of lead).

The following examples will serve further to illustrate the practice and advantages of the invention.

EXAMPLE I Diamines of this invention were blended in a 100 octane aviation fuel composed as follows:

35 volume per cent isoparaffinic alkylate 7 volume per cent isopentane 58 volume per cent Midway California straight run gasoline (composed essentially of naphthen and paraffin hydrocarbons and containing less than '5 volume per cent of aromatic hydrocarbons) and containing 4 milliliters of tetraethyl lead (TEL) per gallon. The F-4 rich mixture ratings of these blends were obtained and the results are tabulated below:

Table I ANTI-KNOCK VALUES OF N,N-DIMETHYL-p-PHENYL- ENE DIAMINE IN A BASE FUEL CONTAINING 4 ML. OF TEL PER GALLON Improvement lf 11-4 Rich in F-4 Rich Rating- Rating due to i f Perfrimance PAdditive- 0. er ormance diammc EXAMPLE 2 Unleaded fuels were also prepared by blending the aviation fuel of Example 1, and N,N'-dimethyl-p-phenylene diamine. F-4 ratings were obtained as shown in Table 11' below:

Table II ANTI-KNOCK VALUES OF UNLEADED BASE FUELS N,N-DIMETHYL-p-PHENYLENE DIAMINE UNDER This application is a continuation-in-part of application Serial No. 792,349, filed December 17, 1947, for Diamines as Rich Mixture Additives, now abandoned.

Having thus described and presented examples of the composition of this invention, it will be understood that this invention embraces such other variations and modifications as come within the spirit and scope thereof.

We claim:

1. A spark ignition engine fuel comprising a base fuel of hydrocarbons boiling in the gasoline boiling range substantially free of gum-forming constituents as measured by ASTM D381-49 and ASTM D873-49 methods below about 6 mg. of gum per ml, not greater than about 6 cc. per gallon of tetraethyl lead, and having an F-Z octane number above about 100 blended with 0.1- 10% by weight of N-methylated phenylene diamines, wherein said diamines have no substituents other than nuclear alkyl groups containing 1 to 4 carbon atoms, inclusive.

2. A spark ignition engine fuel of improved rich mixture characteristics comprising a base fuel of petroleum hydrocarbons boiling in the gasoline boiling range substantially free of gumforming constituents as measured by ASTM 13381-49 and ASTM D873-49 methods below about 6 mg. of uninhibited gum per 100 ml., up to about 4.6 cc. per gallon of tetraethyl lead blended with 0.1-10% by weight of N-methylated phenylene diamines having no substituents other than nuclear alkyl groups containing 1 to 4 carbon atoms, inclusive.

3. A spark ignition engine fuel of improved rich mixture rating comprising a predominant pro portion of substantially gum-free hydrocarbons as measured by ASTM D381-49 and ASTM D873-49 below about 6 mg. of gum per 100 ml.

and boiling in the gasoline boiling range consisting of a blend of at least two members of the group consisting of straight run gasoline, catalytically recracked gasoline, alkylate boiling in the gasoline boiling range, catalytically reformed gasoline, natural gasoline, hydrogenated polymers boiling in the gasoline range, aromatic hydrocarbons boiling in the gasoline boiling range, isopentane, butane, and 2,2,3-trimethylbutane, not greater than about 4.6 cc. per gallon of tetraethyl lead, and having an F-2 octane number of at least about 100 blended with 01-10% by weight of N-methylated phenylene diamines having no substituents other than nuclear alkyl groups containing 1 to 4 carbon atoms, inclusive.

4. The fuel of claim 3, wherein said diamine is N,N'-dimethyl-p-phenylene diamine.

8 a 5. The fuel of claim 3, wherein said diamine is N,N-dimethyl-o-phenylene diamine.

6. The fuel of claim 3, wherein said diamine is N,N'-dimethyl-o-diamine-4-methylbenzene.

7. The fuel of claim 3, wherein said diamine is EN,N'-dimethyl-m-diamine-G-methylbenzene.

References Cited in the file of this patent UNITED STATES PATENTS Von Bramer Mar. 2, 1948 

1. A SPARK INGNITION ENGINE FUEL COMPRISING A BASE FUEL OF HYDROCATBONS BOILING IN THE GASOLINE BOILING RANGE SUBSTANTIALLY FREE OF GUM-FORMING CONSTITUENTS AS MEASURED BY ASTM D381-49 AND ASTM D873-49 METHODS BELOW ABOUT 6 MG. OF GUM PER 100 ML., NOT GREATER THAN ABOUT 6 CC. PER GALLON OF TETRAETHYL LEAD, AND HAVING AN F-2 OCTANE NUMBER ABOVE ABOUT 100 BLENDED WITH 0.110% BY WEIGHT OF N-METHYLATED PHENYLENE DIAMINES, WHEREIN SAID DIAMINES HAVE NO SUBSTITUENTS OTHER THAN NUCLEAR ALKYL GROUPS CONTAINING 1 TO 4 CARBON ATOMS, INCLUSIVE. 